Abstract: Bolt axial force is an important indicator of its working state in coal mine tunnel. The current detection means can not able to carry out random, rapid, non-destructive testing technology. In this paper, the relationship between horizontal natural frequency of anchoring system and bolt axial force has been established based on the principles of structural dynamics. By means of the dedicated electro-hydraulic servo system of bolt tensile testing, the influence of bolt diameter, anchoring state and surrounding rock conditions on the lateral vibration frequency of anchoring system and bolt axial force has been measured. The results show that the lateral vibration frequency of bolt anchoring system and bolt axial force have a good correlation, and the surrounding rock condition is one of the main factors affecting the lateral vibration frequency. The relationship between lateral vibration frequency and bolt axial force can be described by logarithmic function. Base on research founds, the nondestructive testing technology of bolt axial force has been developed. The field application shows that the technology can randomly, non-destructively detect the axial force of bolt in the tunnel.

Key words: bolt axial force, vibration frequency, non-destructive testing, surrounding rock properties